Feedback - An interaction mechanism between processes is called a feedback. When the result of an initial process triggers changes in a second process and that in turn influences the initial one. A positive feedback intensifies the original process, and a negative feedback reduces it.

Feed-in tariff - The price per unit of electricity that a utility or power supplier has to pay for distributed or renewable electricity fed into the grid by non-utility generators. A public authority regulates the tariff.

Flaring - Open air burning of waste gases and volatile liquids, through a chimney, at oil wells or rigs, in refineries or chemical plants and at landfills.

Food security - A situation that exists when people have secure access to sufficient amounts of safe and nutritious food for normal growth, development and an active and healthy life. Food insecurity may be caused by the unavailability of food, insufficient purchasing power, inappropriate distribution, or inadequate use of food at the household level.

Forest limit/line - The upper elevational or latitudinal limit beyond which natural tree regeneration cannot develop into a closed forest stand. It is typically at a lower elevation or more distant from the poles than the tree line.

Fossil fuel emissions - Emissions of heat-trapping gases (greenhouse gases) resulting from the combustion of fuels from fossil carbon deposits such as oil, gas and coal.

Freshwater lens - A lenticular fresh groundwater body that underlies an oceanic island. It is underlain by saline water.

Frozen ground - Soil or rock in which part or all of the pore water is frozen (Van Everdingen, 1998). Frozen ground includes permafrost. Ground that freezes and thaws annually is called seasonally frozen ground.

Fuel cell - A fuel cell generates electricity in a direct and continuous way from the controlled electrochemical reaction of hydrogen or another fuel and oxygen. With hydrogen as fuel it emits only water and heat (no CO2) and the heat can be used (see co-generation).

Fuel switching - In general, this is substituting fuel A for fuel B. In the climate-change discussion it is implicit that fuel A has lower carbon content than fuel B, e.g., natural gas for coal.

Full-cost pricing - Setting the final prices of goods and services to include both the private costs of inputs and the external costs created by their production and use.

Functional extinction - This term defines a species which has lost its capacity to persist and to recover because its populations have declined to below a minimum size. See committed to extinction.

References

Glossaries of the contributions of Working Groups I, II and III to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report 2007.